Fair Value Measurements (Tables)

6 Months Ended

Sep. 30, 2012

Fair Value Measurements [Abstract]

Assets and liabilities measured at fair value on a recurring basis

	September 30, 2012
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	2,414	$	—	$	—	$	2,414
Marketable Securities:
Municipal commercial paper and demand notes		—		65,866		—		65,866
Corporate commercial paper		—		9,179		—		9,179
Holdings of New GM Securities:
New GM Common Stock		665,610		—		—		665,610
New GM Warrants		586,211		—		—		586,211
Total Assets	$	1,254,235	$	75,045	$	—	$	1,329,280
Liabilities:
Liquidating distributions payable	$	54,757	$	—	$	—	$	54,757

	March 31, 2012
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents:
Money market funds	$	38,396	$	—	$	—	$	38,396
Marketable Securities:
Municipal commercial paper and demand notes		—		25,253		—		25,253
Corporate commercial paper		—		59,317		—		59,317
U.S. government agency bonds		—		2,001		—		2,001
Holdings of New GM Securities:
New GM Common Stock		770,389		—		—		770,389
New GM Warrants		759,873		—		—		759,873
Total Assets	$	1,568,658	$	86,571	$	—	$	1,655,229
Liabilities:
Liquidating distributions payable	$	31,720	$	—	$	—	$	31,720